The present invention relates generally to a detector arrangement for use in an optical system and more particularly to an improvement relating to the detector arrangement found in my copending application Ser. No. 912,688, filed June 5, 1978, my copending application Ser. No. 23,866, filed Mar. 26, 1979, my copending application Ser. No. 23,865, filed Mar. 26, 1979, and the copending application of Stauffer and Wilwerding Ser. No. 16,595, filed Mar. 1, 1979.
In the above-mentioned copending applications, radiation from a remote scene to be focused upon is directed by an objective lens to a plurality of lenslets mounted proximate the image of the objective lens. Each lenslet produces an image of the exit pupil of the objective lens and proximate the image plane of each lenslet is mounted a pair of radiation sensitive detectors which produce output signals usable for range determination or auto focussing of cameras. The image of the exit pupil is generally circular in nature or, in the case of the above-mentioned copending application Ser. No. 23,866, oblong or oval. It is desirable that the detectors be as large as possible to maximize the signal available for range determination but are generally rectangular for ease of production. The rectangular detectors are mounted in pairs so that they fit within the entire circular or oblong image of the exit pupil. The size of the image varies with the f number of the objective lens and since the most commonly used lenses have a maximum aperature in the range of f/1.4 to f/2.8, the size of the detectors is chosen so that they will fit entirely within the image produced by an f/2.8 lens. In some cases, however, it is desirable to uses lenses that have an f number greater than 2.8 as, for example, a telephoto lens which may have an aperture as small as f/4.0. When this occurs, the image of the objective lens pupil is smaller than the detectors and errors in detector output may occur.